Marty, I built an ST70 over the summer, and am delighted with it. It was fun, fast, and I often stay up late at night with a smile on my face listening to it. Of course, it's not the most powerful amp out there, or anywhere near it, and the low frequencies leave a lot to be desired, but in all honesty, I'm not really sure any of the amplifiers I've been around really surpass it in the midrange or in the total sense of musical enjoyment.
It took me getting an old set of 7199 drivers before it really lit my fire (the Sovteks really suck, and I've never heard a bigger tube improvement in audio than rolling this tube), and I'm told I need to upgrade the 5AR4 rectifier as well, though I haven't yet done that. The only upgrades I did were the input jacks, loudspeaker terminals, and power supply cap, all of which I got from Bob Latino, everything else came from Kevin. I also bought an upgraded driver board kit from Bob, but I'm so satisfied with the amp currently, I never felt the need to assemble it or make a few of the tweaks such as converting it to triode operation (more romantic) or lowering the values of the cathode bias resistors (supposed to really open up the sound). Obviously, I'd contact Kevin at DynaKit parts and/or Bob Latino about getting one.
Interesting to note how far we have not come in the past 50 years.